On page 144 of our first volume I gave you a brief account of the great airship invented by Count Zeppelin and called after his name. It is said that the newest type of Zeppelin is about 700 feet long, and has eighteen compartments, which hold about a million cubic feet of hydrogen. Each compartment is a separate balloon, and in theory the airship can remain afloat if two of the balloons are damaged. The framework is of wood and aluminium. The engines, guns, stores, and crew are contained in two cars or gondolas, which are built into the framework of the airship, almost flush with its keel. The engines are four in number, and drive the propellers, a pair being coupled to each car, two forward and two astern. When they are working they make a terrible din, and a Zeppelin thus advertises his approach. Some of the latest vessels have a speed of from forty to sixty miles an hour. Two sets of rudders are provided--one set for steering the ship horizontally, and one set to guide it when ascending or descending. It can ascend with remarkable speed--it is said that a modern Zeppelin can soar upwards at a speed of 4,500 feet per minute, and can reach the safety zone of about 12,000 feet almost before artillery on the ground has secured the range. A large Zeppelin can carry about seventeen tons, of which about two tons consist of explosives. All Zeppelins are fitted with powerful searchlights, and a car which can be let down from the gondola by steel ropes so as to enable the men in it to make observations from a lower level. The weakest part of a Zeppelin is its upper envelope. Attacking aeroplanes always endeavour to rise above the airship in order to drop bombs upon it. You will remember that Warneford destroyed his Zeppelin in this way. [Illustration: Sub-Lieutenant Warneford bombing a Zeppelin in Mid-air. (_By permission of The Graphic._) A description of this exploit, which won Sub-Lieutenant Warneford the Victoria Cross, is given on page 382.] Before the war a Zeppelin had travelled 1,800 miles on a single journey, and had remained in the air for thirty-five hours at a stretch. I have already told you that the Germans had built great airship sheds on the island of Heligoland. From this base to Yarmouth, on the east coast of England, is a distance of only 280 miles. It was, therefore, clear that, given suitable weather, a Zeppelin could not only cross the North Sea and return, but could sail over large areas of Great Britain as well. The Germans had long dreamed of making Zeppelin raids on London and destroying it by means of big bombs; but most people in this country laughed at the notion. We pinned our faith to the aeroplane, and believed the Zeppelin to be little more than an expensive failure. No real efforts were, therefore, made to cope with the threatened danger. A few anti-aircraft guns were stationed round the capital, searchlights were installed, street lamps were obscured, and windows were darkened, but that was all.